Bills of attainder are legislative acts passed for the special
purpose of attainting particular individuals of treason, or
felony, or to inflict pains and penalties beyond, or contrary
to the common law. They are state-engines of oppression
in the last resort, and of the most powerful and extensive
operation, reaching to the absent and the dead, as well as
to the present and the living. They supply the want of legal
forms, legal evidence, and of every other barrier which
the laws provide against tyranny and injustice in ordinary
cases: being a legislative declaration of the guilt of the
party, without trial, without a hearing, and often without
the examination of witnesses, and subjecting his person to
condign punishment, and his estate to confiscation and
forfeiture. Instances of their application to these nefarious
purposes occur in almost every page of the English history
for a very considerable period: and very few reigns have
passed in which the power has not been exercised, though,
to the honour of the nation, I believe, no instance of the
kind has occurred for more than half a century.

In May, 1778, an act passed in Virginia, to attaint one
Josiah Philips, unless he should render himself to justice,
within a limited time: he was taken, after the time had
expired, and was brought before the general court to receive
sentence of execution pursuant to the directions of
the act. But the court refused to pass the sentence, and he
was put upon his trial, according to the ordinary course of
law. . . . This is a decisive proof of the importance of the
separation of the powers of government, and of the independence
of the judiciary; a dependent judiciary might
have executed the law, whilst they execrated the principles
upon which it was founded.

If any thing yet more formidable, or more odious than
a bill of attainder can be found in the catalogue of state-enginery,
it is what the constitution prohibits in the same
clause, by the name of ex post facto laws: whereby an action
indifferent in itself, and not prohibited by any law at the
time it is committed, is declared by the legislature to have
been a crime, and punishment in consequence thereof, is
inflicted on the person committing it. Happily, for the
people of Virginia, I can not cite any case of an ex post facto
law, (according to this definition, which I have borrowed
from Judge Blackstone,) that has been made in this commonwealth,
nor have I heard of any such, in any other of
the United States, that I recollect.

Tucker, St. George. Blackstone's Commentaries: With Notes of Reference to the Constitution and Laws of the Federal Government of the United States and of the Commonwealth of Virginia. 5 vols. Philadelphia, 1803. Reprint. South Hackensack, N.J.: Rothman Reprints, 1969.